1. Field of the Invention
The invention is directed to high-temperature fuel cells for converting chemical energy into electrical energy and relates (1) to the development of electrochemical high-temperature cells using ceramic solid electrolytes as ion conductors, wherein the cells are to a great extent independent of the fuel used and guarantee a compact arrangement and also relates (2), in a narrower sense, to an arrangement, of a multiplicity of flat, planar high-temperature fuel cells assembled into a stack, connected in series, and utilizing zirconium oxide as the solid electrolyte with electrically conductive separation plates placed between the cells.
2. Discussion of the Background
High-temperature fuel cells using doped, stabilized zirconium oxide are known to have numerous embodiments. In flat, planar fuel cells that are lined up into stacks ("filter press principle"), frame-like seals are definitely necessary to be provided on the outer periphery of the plate-shaped elements to press the interconnected components (e.g., bipolar plate, separation plate, current collector), which act to transmit the current perpendicular to the plate plane, on the adjacent electrodes and to guarantee perfect contact. As a rule, these electrically insulating, frame-like seals are made so that their main planes lie parallel to the plate plane of the adjacent element.
This layering of fuel cells, separation plates and flat, frame-like seals leads to a repeatedly statically indeterminate system which is difficult to control in practice. Either the contact pressure of the parts that are to guarantee the electrical contact is found to be insufficient or the pressure on the seal is insufficient for gas-tight closure. In addition, these flat seals make the feeding and removal of the gaseous media at the edges of the plate-shaped fuel cells more difficult and lead to an expensive structural configuration.
The following publications and patents are known prior art:
O. Antonsen, W. Baukal and W. Fischer, "Hochtemperatur-Brennstoffbatterie mit keramischem Elektrolyten" ["High-temperature Fuel Battery with Ceramic Electrolyte"], Brown Boveri Mitteilungen [Information] January/February 1966, pages 21-30,
U.S. Pat. No. 4,692,274
U.S. Pat. No. 4,395,468
W. J. Dollard and W. G. Parker, "An Overview of the Westinghouse Electric Corporation Solid Oxide Fuel Cell Program," Extended Abstracts, Fuel Cell Technology and Applications, International Seminar, The Hague, Netherlands, Oct. 26 to 29, 1987,
F. J. Rohr, High Temperature Fuel Cells, Solid Electrolytes, 1978 by Academic Press, Inc., page 431 ff,
D. C. Fee et al., Monolithic Fuel Cell Development, Argonne National Laboratory, paper presented at the 1986 Fuel Cell Seminar, Oct. 26-29, 1986, Tucson, Ariz, U.S. Department of Energy, the University of Chicago.
The previously known arrangements of fuel cells and components placed between them are unsatisfactory in practice in many respects. Therefore, there is a great need to create more definite and simpler conditions with respect to statics, thermal expansion and manufacturing technology.